Ho-Ho-Hold On! Inconsistencies Observed in Advertised Aminosilane Coating Uniformity

Background

Experiments involving cDNA/PCR often use aminosilane treated glass as a substrate. These experiments often produce results that are not as expected. Our analysis shows that the issue may lie very early on in the process, from the preparation of the glass itself. Instead of a substrate comprised of glass with an even coat of aminosilane, our technique has uncovered that the aminosilane forms small islands that coat only about 1% of the glass.

Results

An aminosilane coated glass was analyzed with our PiFM technology, and the results are shown in figure 2 (a chemical map), and figure 3 (PiF-IR point spectra from six locations identified in figure 1). From figure 3, you can see that the point spectra from the substrate, in red and green, look just like the spectrum from the reference glass (the dashed dark blue line) without the treatment, except for the increased intensity between 2800 to 2000 cm⁻¹, and most importantly, without any amine signatures at around 1630 cm⁻¹. Only the aggregates show the amine peaks. This points to an issue with the substrate itself, and therefore, an error is introduced very early on.

The Discrepancy

Traditional spectroscopy methods will correctly identify the presence of aminosilane, but lack the spatial resolution required to see how well coated the glass substrate is.  For example, techniques such as XPS, glancing angle FTIR, ellipsometry, and water contact angle will all sample a much larger area and will not be able to verify whether or not the substrate is uniformly covered with a monolayer.

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